I'm curious, what type of radar is used in spy satellites? Is there any health risk for people on the ground?
China: http://en.wikipedia.org/wiki/Yaogan
US: http://en.wikipedia.org/wiki/Lacrosse_%28satellite%29
Germany: http://en.wikipedia.org/wiki/SAR-Lupe
I was slightly surprised to find out that Germany has such an extensive system of military spy satellites!
(http://en.wikipedia.org/wiki/E-8_Joint_STARS)
Basically, they can identify tanks, buildings, and other large objects via radar. There are also millimeter band radars that can produce images.
The same kind as on aircraft, basically. Synthetic aperture is one form of radar that's been in use for a while, and I'm sure it's progressed by amazing levels since I was in the game.
Is there any health risk for people on the ground?
Nope, not much more RF radiation that what we get zapped with by terrestrial radiation.
not to mention that there are definitely more than 1 radar in 300km radius of you than this.